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1. Introduction
1.1 Description
The Mark 25 Dissolved Oxygen Analyzer is a simple, low cost, 4 channel,
microprocessor-based monitoring system designed for ultrapure water applications. The
system consists of a readout module that can be used with up to four galvanic-style
dissolved oxygen sensors; each sensor being placed into a separate flow chamber.
A large 4 digit LED display indicates either temperature, parts-per-million (ppm) or
parts-per-billion (ppb) dissolved oxygen. An 8-key membrane keypad allows the
operator to quickly setup and calibrate the analyzer.
The Mark 25 measures dissolved oxygen in four ranges; 0-20 ppb, 0-200 ppb, 0-2
ppm, and 0-20 ppm. Automatic calibration within the Mark 25 provides a fairly reliable
measurement. However, comparison to a referee system remains the most accurate
method of calibration available. (Please refer to Martek's Mark 21 Portable Dissolved
Oxygen Analyzer for further information).
Four alarm set points with relay contacts are standard in addition to four analog
recorder outputs (0-20 mA) and a serial RS232 digital output for hookup to external
recording equipment. For maximum flexibility, alarm set points and analog outputs
can be assigned to any range on any parameter on any channel.
Housed in a ¼ DIN corrosion-resistant plastic case, the readout module can be panel
mounted with a minimum of tools. The analyzer accepts power inputs from 97 to 240
VAC 50/60 Hz or 24 Vdc and comes with an ON/OFF switch located on the rear panel.
Alarm and recorder wires are easily installed in removable terminal strips.
Sensors connect via a DB-9 connector located on the rear panel of the Mark 25 and the
sensors mount easily to any flat surface. In addition, Martek offers adapter plates
specifically designed to cover the space occupied by other brands of conductivity
analyzers.
Sensors come standard with 6 feet (2 meters) of cable.
3
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